1. Field of the Invention:
The present invention relates generally to color photography and particularly to a color photographic material containing a novel colored coupler in a photographic emulsion layer thereof.
2. Description of the Prior Art:
It is well known that the so-called couplers, that is to say, compounds capable of forming dyes such as indophenols, indoanilines, indamines, azomethines, phenoxazines, phenazines, etc., by a coupling reaction with oxidized primary aromatic amine developing agents are used in color photographic materials containing silver halide emulsion layers.
On the other hand, a silver halide color photographic material based on the subtractive three primary color principle has, as a layer structure, a silver halide emulsion layer to form a yellow color by the action of blue light, a silver halide emulsion layer to form a magenta color by the action of green light, and a silver halide emulsion layer to form a cyan color by the action of red light. When a color forming system wherein a primary aromatic amine developing agent and couplers are used is applied for color image formation of such a color photographic material, an acylacetamide derivative or a dibenzoylmethane derivative is usually used as the yellow forming coupler, a 5-pyrazolone derivative, a cyanoacetyl derivative, an indazolone derivative, or a pyrazolonebenzimidazole derivative is usually used as the magenta forming coupler, and a phenol derivative or an .alpha.-naphthol derivative is usually used as the cyan forming coupler.
In a color photographic material based on the subtractive three primary color principle, it is ideal that the yellow forming image absorbs blue light only, the magenta forming image absorbs green light only, and the cyan forming image absorbs red light only. However, the color images obtained in silver halide color photography using the above-described couplers are not always ideal and the color forming images usually have secondary absorptions and frequently absorb undesired light. It is known to use a so-called masking method employing colored couplers for correcting the secondary absorption deficiency of the color forming images as described in, e.g., PSA Journal, Vol. 13, 94(1947).
The color image formed by using a 5-pyrazolone derivative as a magenta-forming coupler has a secondary absorption in a blue region at about 440 nm in addition to the main absorption in a green region at about 550 nm. It is also well known to use a 5-pyrazolone having an arylazo group at the 4-position as a yellow colored coupler for correcting the secondary absorption color deficiency.
It is desired that the colored coupler used for the aforesaid masking system has sufficient light absorption characteristics for correcting the secondary absorption deficiency of the color forming images as well as sufficient development activity.
In the specifications of U.S. Pat. Nos. 2,428,054 and 2,449,966 a 1-phenyl-3-acylamino-4-phenylazo-5-pyrazolone is described as a colored coupler but a colored coupler of this type has a low development activity and hence in order to obtain sufficient masking using such a colored coupler, a large amount of the colored coupler is required, which results in reducing the sensitivity of the color photographic material containing the coupler.
Also, in the specification of U.S. Pat. No. 2,983,608 a 1-phenyl-3-anilino-5-phenylazo-5-pyrazolone is described as a colored coupler but although this colored coupler has a high development activity as compared to that of the above-described 3-acylamino type coupler, the colored coupler has a broad light absorption spectra and has a large undesired absorption of green light.
British Pat. No. 1,044,778 discloses a 1-phenyl-3-(2-halogenoanilino)-4-phenylazo-5-pyrazolone but this coupler has difficulties in that the coupler has a water-solubilizing group in the molecule and thus the treatment of such a coupler in the case of producing color photographic materials is troublesome and in that the coupler has a broad light absorption spectra and has a large undesired absorption in a green region.
Furthermore, in the specification of U.S. Pat. No. 3,615,506 the colored coupler having the following formula ##STR2## is described.
This coupler is, however, insufficient in development activity and also exhibits a large undesired absorption in a green region in the light absorption spectra thereof. Furthermore, .alpha.-naphthylamine is used as a raw material for preparing the coupler but the raw material contains .beta.-naphthylamine which is a carcinogenic substance and thus such a material possesses handling difficulties from the view point of health.
As described above, pyrazolone type colored couplers which have hitherto been known have various specific difficulties in addition to low development activity as a common difficulty. The development activity of the colored coupler contributes greatly to the development speed of photographic emulsion layers containing the colored coupler and thus sufficient development speed cannot be obtained using such a conventional 5-pyrazolone type colored coupler. This difficulty is a large obstacle in shortening the development period for color photographic materials.